Modulation error ratio (MER) is used as a measure of the signal to noise ratio (SNR) in many communications systems. In general, MER measurements are based on errors between received symbols and constellation symbols closest to those received symbols in an associated constellation diagram. The difference between a received symbol and a closest constellation symbol can be referred to as a slicer error.
Generally, MER can be calculated as the ratio of the energy of a target symbol to the energy of the error between the target symbol and a received symbol. For example, when the target symbol is the closest constellation symbol as described above, the MER can be calculated by dividing the energy of the closest constellation symbol by the energy of the slicer error.
An MER measurement can represent an approximation of the SNR in a communication system. However, the accuracy of an SNR approximation can be diminished when a received symbol is sliced incorrectly. For example, an MER measurement may not accurately reflect SNR where the closest constellation symbol to a received symbol is improperly identified as the target symbol in the MER measurement.
Like reference numbers and designations in the various drawings indicate like elements.